The present invention relates to, in general, a solid-state image sensor and more particularly a solid-state image sensor of the type in which a photoconductive layer or a photosensor is formed over a semiconductor circuit substrate capable of charge transfer or having the switching function.
There have been devised and demonstrated solid-state image sensors of the type comprising, in combination, a photoconductive layer or a photosensor and a matrix of BBD or CCD unit cells capable of charge transfer or an X-Y matrix of MOS switches of the type in which X- and Y-shift registers read out the stored charge. In the solid-state image sensor of the type described above, each picture element is provided with one first electrode which is connected to the photoconductive layer or photosensor and to its associated region which is formed within the bulk of the semiconductor circuit substrate and which is opposite in conduction type to the semiconductor substrate, the region being referred to as "the diode region" in this specification. The incident light which has not been absorbed in a transparent electrode and a photoconductive layer is transmitted through the gaps or spaces between the first electrodes to the semiconductor substrate, resulting in the generation of electron-hole pairs. The holes move through the semiconductor circuit substrate but the electrons flow into the diode regions where the photocharge is stored, into the BBD or CCD charge transfer channels or into the drains of MOS switches. That is, in the case of BBD or CCD, the unwanted charge electrons migrate into the signal electrons, causing a blooming effect. In the case of the X-Y matrix type solid-state image sensor, the drains of the MOS switches in each column are all electrically connected with each other. As a result, the unwanted electrons which flow into the drains also cause blooming; that is, a phenomenon that the signals appear where they should not.
In the conventional solid-state image sensor, each unit cell is coated with an aluminum layer except a light receiving area or color separation filters are coated with metallic (aluminum) light-shielding layers. In general, the aluminum layers have a higher degree of coefficient of reflection, so that the light rays reflected back from the aluminum layers are again reflected back from the surface of the camera lens to the light receiving areas, thus adversely affecting the optical information read-in operation.